In the tractor manufacturing industry, a front axle is known, in which, in addition to the front wheels steering the vehicle, the axle itself performs a relative roto-lateral movement with respect to the chassis to improve steering performance. A certain amount of vertical movement of the front wheels must also be allowed to adapt to rough ground.
Though a big improvement with respect to conventional systems, currently used steering systems employing relative lateral movements with respect to the chassis pose the problem of the wheels, at certain wheel tilt angles, colliding with the front of the tractor. Moreover, many currently used tractors, particularly so-called “supersteer” types, have no front suspensions. In this type of vehicle, the front axle has fork members for supporting a front ballast, or a front implement, or a front power take-off (PTO). In these applications, when turning, all the mechanical devices (front ballast, front implement, PTO, etc.) are turned together with the front axle and so prevented from interfering with the front wheels.
However, to fit a tractor with front suspensions, e.g. to increase operating speed and adapt to rough ground, the front mechanical devices must be mounted directly on the chassis, as opposed to the front axle, thus resulting in interference between the front wheels and the front mechanical devices when turning. In other words, in motor-vehicles with suspensions, the front devices (ballast, front implement, front PTO, etc.) can no longer be mounted on the front axle. In fact, the front axle being equipped with suspensions, the front devices, if they were to weigh directly on the front axle, would necessarily have to follow the contour of the terrain, thus at least partly forfeiting the advantages for which a front suspension system is provided in the first place. In motor-vehicles with front suspension systems, therefore, the front devices must be mounted directly on the chassis, as opposed to the front axle.
It should be stressed, therefore, that, though the present invention applies in particular to motor-vehicles with front suspensions, the teachings of the invention also apply to advantage to motor-vehicles with no front suspensions.